The invention is directed to an infrared emitter element having:                at least one emitter tube made of silica glass, which has two ends,        at least one electrical conductor arranged in the emitter tube as a radiation source,        a cooling tube made of silica glass, which surrounds the at least one emitter tube spaced therefrom and which is connected to the at least one emitter tube at its ends, so that in the region of the electrical conductor, at least one flow-supporting channel is formed between the at least one emitter tube and the cooling tube, and        a metallic reflector.        
The invention is further directed to the use of such an infrared emitter element.
Infrared emitter elements mentioned above are known, for example, from German published patent application DE 100 41 564 A1. This publication discloses a cooled infrared (IR) emitter element, wherein FIGS. 5a to 6c show IR emitters sheathed by a silica-glass cooling tube and contacted on two ends. A coolant for cooling the IR emitters is provided for flow through the space between the cooling tube and the IR emitters. In the cooling tube, a reflector is located adjacent to the areas of the IR emitters that emit radiation, through which reflector a portion of the coolant can flow, without the IR radiation affecting this portion of the coolant. The IR radiation, which is emitted by the IR emitters, is led either directly through the radiation-permeable coolant and the silica-glass cooling tube or is first reflected by the reflector and then intersects the path through the cooling tube before it strikes the body to be treated.
International patent application publication WO 98/31045 discloses a heater for ultra-pure, de-ionized water with a cylindrical heating element, which is arranged between two tubes made of quartz glass. Inside and outside of this heating arrangement is a further respective tube made of quartz glass, whereby a first and a second annular flow channel is formed for the water to be heated. At the ends of the tubes, the tubes are connected by end caps made of plastic. The water flows from the first flow channel into the second, so that it flows once inside of and once outside along the cylindrical heating element. The heating of the water thereby results through heat conduction, convection, and radiation. A laminar flow is maintained in the flow channels in order to keep the erosion of the tubes by the water low. However, this also leads to the fact that the heat exchange is less effective. The arrangement is complicated, expensive, and difficult to seal due to the plurality of required components. The end caps, by which the four tubes made of quartz glass with different diameters are to be sealed, are formed of plastic and come in direct contact with the water to be heated. This is particularly disadvantageous because plastics can lead to contamination of the water with bacteria.
U.S. Pat. No. 5,054,107 describes a device for heating fluids by infrared radiation. Here, gas-flushed infrared emitters, consisting of a heat conductor in a jacket tube, are provided for heating ultra-pure water, which flows through a vessel made of quartz glass or PTFE. The vessel here can have a reflector, which reflects back into the water the radiation emitted by the infrared emitters and not absorbed directly by the water. A direct contact between the fluid to be heated and the jacket tube of the infrared emitter is not provided, so that the heating of the fluid must result only through radiation. In addition, cooling of the infrared emitter, the housing, and the reflector is required. The additional cooling of these components leads to heat losses and can represent a source for contamination of the ultra-pure fluid. Because the cooling efficiency for the cooling of the infrared emitter is poor, the output of this heat exchanger is limited. The preferred wavelength to be emitted by the infrared emitter is disclosed to be that of the maximum absorption of water at 3 μm. However, infrared radiation of this wavelength cannot penetrate far into the water and leads to non-uniform heating.